Researchers used tiny vibrating "microcantilevers," like the one pictured here

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Microcantilever, Pathogens, Purdue University

Researchers in the US have improved the performance of sensors that detect chemical and biological agents such as pathogens, potentially benefiting the food processing industry.

The sensors measure amplitude instead of frequency by using tiny vibrating microcantilevers, slivers of silicon shaped like small diving boards, said scientists from Purdue University.

The amplitude was recorded by how far the sensors moved when particles landed on the microcantilever.

This could be used in food processing equipment to identify the quality of the food and eliminate E.coli and other potentially damaging vapours, said the study published in the Journal of Microelectromechanical Systems.

Microcantilevers vibrate at their natural, or "resonant", frequency. Analysing the frequency change when a particle lands on the microcantilever, reveals the particle's presence and potentially its mass and composition.

The findings show that the new smaller sensors should be capable of more reliably measuring smaller quantities of gas than is currently possible, said the research entitled “Modeling, Analysis, and Experimental Validation of a Bifurcation-Based Microsensor”.

Cut down on waste

George Chiu, mechanical engineering professor at the university told FoodProductionDaily.com that the findings could potentially reduce costly recalls as well as waste in the food processing sector.

“Because the size and sensitivity of the sensor and detection mechanism, it can potentially be developed into in situ monitoring systems in the food processing processes with the benefit of identifying potential issues during the process,” he said.

“The size and sensitivity of the sensor can potentially be implemented as a sensor/monitoring system within a package that can realise a complete monitoring system covering processing, handling and storage among the producer, distributor and consumer.”

Jeffrey Rhoads, assistant professor of mechanical engineering, told this publication the patent-pending research could “move towards a commercial product that can be used in a variety of contexts.”

“Our particular sensors utilise a nonlinear phenomenon which allows us to measure changes in amplitude instead of resonant frequency.”

Rhoads said: “This, in turn, allows to feasibly build smaller, potentially more sensitive devices, which we haven’t done yet, and also to minimise false detection rate, which we have done.

“In general, the benefits of cantilever-based microsensors are small scale, lower power consumption, ease of integration with existing electronic systems, and high sensitivity, i.e. they can detect very small amounts of substance.

“Perhaps the biggest impediment to this research direction is that it goes against the current nanosystem design paradigm, which encourages engineers to build linear devices, i.e. devices where the response is proportional to the input.

Next step to test liquids

“Currently we have optimised our devices to operate in a gaseous environment, but we are moving towards operation in liquid environments,“ Rhoads said.

Source: The Journal of Microelectromechanical Systems

Published online ahead of print, doi: 10.1109/JMEMS.2011.2182502

“Modeling, Analysis, and Experimental Validation of a Bifurcation-Based Microsensor”